In general, leisure watercrafts, such as motorboats, are stored on the sea inside marinas, or in boat yards or boathouses on land when they are not used. In order to use watercrafts stored on the sea, there is no need to carry the watercrafts to the sea, and users simply get on and pilot the watercrafts. This is simple and easy. However, the rent for mooring is high, and care is necessary, for example, when high waves are caused by a typhoon. In contrast, when a watercraft is stored on land, it is carried onto the sea with much labor and manpower because, in many cases, a boat yard is located away from the shore, or watercrafts are stacked in a boathouse even when the boathouse is near the shore. Heavy equipment, such as a crane, is sometimes needed, and the carrying operation is troublesome. Accordingly, apparatuses that easily carry a small watercraft stored on land have been proposed.
For example, Japanese Unexamined Patent Application Publication No. 5-193559 (hereinafter referred to as Patent Document 1) discloses “a self-propelled platform including a driver and a carriage connected to the driver, wherein the driver includes wheels, a driving means for driving the wheels, and a steering wheel, and the carriage includes wheels, a main body, mounts provided on the main body, and a positioning means for positioning a watercraft at a desired longitudinal position on the mounts”.
In the invention disclosed in Patent Document 1, a small watercraft is loaded on the self-propelled platform, is carried from a storage place to the waterside, and is launched on the water by putting the platform into the water. Conversely, when the small watercraft is carried to the shore, it is transferred onto the platform by putting the platform into the water, and is moved to a predetermined storage place. The small watercraft can be easily hoisted on land and launched on the water. Since the driving means is not provided in the carriage, but is provided in the driver, it does not become wet even when the carriage enters the water, and therefore, does not easily deteriorate.
Japanese Unexamined Patent Application Publication No. 10-181683 (hereinafter referred to as Patent Document 2) discloses “a small-watercraft platform wherein a carriage is provided below a receiver for supporting the bottom of a small watercraft, a rear portion of the receiver is pivotally mounted on the carriage, and a receiver-tilting device is provided near a pivot shaft to tilt and hold the receiver at a predetermined tilting angle”.
In the invention disclosed in Patent Document 2, after the bottom of a small watercraft is widely supported by the tiltable receiver in the water, the small watercraft and the small-watercraft platform are hoisted simultaneously. Therefore, the hoisting operation is safely performed with little influence of wind and waves, and the operation is easy and reliable.
As an apparatus for moving a watercraft up and down on the sea, Japanese Unexamined Patent Application Publication No. 8-216981 (hereinafter referred to as Patent Document 3) discloses “a floating platform including a loading base on which a watercraft is placed, and a pair of tubular floats arranged on both widthwise sides of the loading base, wherein each of the floats is partitioned into front and back airtight chambers, an air supply and exhaust tube and a water supply and exhaust tube are respectively connected to the airtight chambers, and the front and back air tight chambers are nonuniformly divided in the front-back direction”.
In the invention disclosed in Patent Document 3, the tilt of the floating platform in the front-back direction caused by adjusting the buoyancy of the floats in the front-back direction acts as a force that reduces or absorbs the tilt of the floating platform in the right-left direction. Therefore, it is possible to reliably prevent the floating platform from tilting in the right-left direction or turning over when being moved up and down. Even when the floating platform does not turn over, it can be effectively prevented from tilting in the right-left direction, and therefore, a passenger will not panic.
In the conventional arts described in Patent Document 1 and Patent Document 2, certainly, launching and hoisting operations can be easily and safely performed when using a small watercraft, and the small watercraft can be easily carried through a path from a storage space onto the sea and through a reverse path. However, it is basically impossible for one person to perform these operations, and several persons are necessary. Furthermore, since the persons need to get off the watercraft during hoisting, they may soil their feet or may slip at that time. Moreover, at a moment when the watercraft is unloaded from the platform onto the sea or a moment when the watercraft is loaded from the sea onto the platform, it is synchronized with the waves on the sea, while the platform stays at the bottom of the sea. Therefore, it is difficult to load the watercraft on the platform particularly during hoisting.
In contrast, the conventional art described in Patent Document 3 provides the floating platform that prevents the bottom of the watercraft from being soiled with, for example, shells and algae when the watercraft is moored on the sea for a long time. While the floating platform can be moored in a predetermined place such as a marina or a harbor, the watercraft cannot be hoisted therefrom so as to be stored on land, and the floating platform cannot be moored for a long time at an appropriate place on the sea during use of the watercraft.
The present invention has been made to meet such conventional circumstances, and an object of the invention is to provide a self-propelled platform that carries a small watercraft from a storage place on land onto the sea, that can be moored and stored on the sea during use of the small watercraft, and that enables one person to easily, sanitarily, and safely make preparations for use of the small watercraft.